Paper honeycomb core is a desirable building material with a growing range of applications and uses. Paper honeycomb core can be used to make strong lightweight panels and pallets. Paper honeycomb panels are constructed of an expanded honeycomb core or web sandwiched between two paper face sheets.
Two types of machinery are used to produce paper honeycomb core: a rotary cut core machine and a segment cut core machine. Segment cut core machines are the most common and economical to operate. U.S. Pat. Nos. 3,257,253 and 4,133,172 illustrate and describe the basic design and operation of a segment cut core machine. Segment cut core machines produce honeycomb core from rolled sheets of paper stock. The core machine bonds multiple sheets of paper stock together into a continuous sheet of core stock. The core machine then feeds the core stock into a cutting mechanism or shear, which cuts the core stock into strips. As a strip of core stock is sheared off, it is pressed against the previous cut strip and bonded together to form the collapsed honeycomb core.
All segmenting type core machines operate with a certain amount of slack in the core stock entering the cutting mechanism, due to the fact that core stock is continuously fed into the cutting mechanism but the cycling of the cutting mechanism shears and stacks the honeycomb core intermittently. Consequently, segment cut core machines employ a take-up section, where the slack in the core stock gathers before moving into position to be cut. U.S. Pat. No. 3,257,253 granted to Edwin R, Hoyt describes a segment cut core machine that has a horizontally oriented cutting shear and a vertical oriented take-up section. U.S. Pat. No. 4,133, 172 granted to Robert C. Geschwender describes a segment cut core machine that has a vertically oriented cutting shear and a horizontally oriented take-up section.
Often, segment cut core machines, such as the one described in Hoyt '253 include a bow plate and “tensioners” in the take-up section. The bow plates support and guide the gathered core stock within the take-up section and the tensioners apply a gentle force to the gathered core stock, which forces it to advance into the cutting mechanism. Typically, tensioners take the form of a plurality of spring tensioned cords which overlay the core stock in the take-up section and press against the gathered slack in core stock.
Control of the gathered core stock within the take-up section and the cutting process is critical for producing uniform and consistent honeycomb core from segment cut core machines. In segment cut core machines, it is desirable to reduce the time in which the cutting mechanism is closed (the “close time”) during which the core stock is gathered in the take-up section. It is also desirable to control the manner in which the slack in the core stock gathers within the take-up section in terms of a waveform, i.e. wave length and amplitude. Controlling the manner in which the core stock gathers within the take-up section ensures that the core stock is properly and consistently advanced into the cutting mechanism.
Heretofore, conventional segment cut core machines have had several operational draw backs and have generally failed to fully control the manner in which the core stock gathers within the take-up section. Conventional segment cut core machines require extensive, time consuming mechanical adjustment to set up each operational run and to maintain uniform and consistent honeycomb core. The cycle rate of the cutting mechanism must be finely matched to the speed of the core stock advancing from the paper feed to prevent too much or too little slack in the gathered core stock. When too little slack is gathered, the core stock does not advance fully into the cutting mechanism. When too much slack is gathered, the core stock jams and buckles. Paper jams due to excess slack are often the source of operational down time. Buckling the core stock can often damage the laminated sheet of core stock separating the individual piles of paper web. Mechanically matching the cutting cycle to the speed of the core stock feed is also complicated by variations in the core stock. For example, when the core stock gathers in the take-up section, the inherent stiffness in the core stock helps to forceably advance the core stock into the cutting mechanism. Because the stiffness of the core stock may vary considerably (depending on physical properties of the individual sheets of paper stock, which may vary in thickness, changes in humidity and the degree to which the sheets are wet glued), there is a tendency for the stored energy in the buckle to vary. The thickness and stiffness of the core stock also mandates that the bow plate provide a smooth sloping arc into the cutting mechanism to prevent buckling and damage to the laminated core stock. More importantly, conventional segment cut core machines have offered little means for controlling the manner and character of the slack that gathers in the sheet of core stock within the take-up section. Often core stock jams inside the cutting mechanism due to buckles and uneven folds created in the take-up section. Heretofore, the slack has been free to gather and buckle under its own influence. At best, a mechanical adjustment that affects the gathers in conventional core machines has been limited to simply adjusting the amount of force applied to the gathers by the tensioners.